The Section on Clinical Brain Imaging has made a sustained effort to use positron emission tomography (PET) to help elucidate the neural mechanisms and pathophysiology of psychiatric disorders. The major focus of the Section has been directed at using PET to address questions about Attention-Deficit Hyperactivity Disorder (ADHD) in adult and teenage subjects. PET studies related to ADHD were conducted in three areas: Stimulant effects: Studies were completed on the cerebral metabolic effects of acute and chronic dextroamphetamine and methylphenidate treatment. Both stimulants appear to have modest metabolic effects in the brain while producing positive behavioral improvement. Development: PET studies on normal teenagers and those with ADHD and schizophrenia are continuing. A new method, which allows minors to be scanned with minimal radiation, is being employed and the initial description of the procedure has been accepted for publication. In addition, teenagers with schizophrenia are being scanned by our Section using the new method. Thyroid: Resistance Symptoms of ADHD are highly associated with generalized resistance to thyroid hormone, a disorder with a defined genetic defect. PET studies show impaired attention and reduced metabolism in the parietal lobe. The Section is continuing studies on scopolamine as a model for the memory impairment in Alzheimer's Disease. Initial results show altered metabolism in brain areas related to memory function. The Section is continuing work on the development of F-DOPA methodology, which is now extended to human subjects after initial work with primates. Using primate model, studies are continuing on metabolic effects of cocaine and fluphenazine. Finally, the Section is continuing its mission to train other research groups in the use of PET imaging technology and data analysis.